1. Field of the Invention
The present invention relates generally to a camera and, more particularly, to a camera in which a picture size is changed over in accordance with a magnitude of an image circle of a photographing lens to be installed.
2. Related Art Statement
The present inventor previously proposed, to the Japanese Patent Office, cameras which are, as disclosed in Japanese Patent Application Nos. 200877/1991 and 201969/1991, adapted to change over a photographing picture size and capable of photographing with a photographing picture larger than the current JIS-135 type film having perforations by use of a film with no perforation (hereinafter called an S-format film) for the purpose of improving picture quality thereof, i.e., this film being conceived as a roll film which employs the current JIS-135 type film and a Patrone of this current JIS-135 type film.
In these cameras, an existence or non-existence of the perforations of the film loaded in a camera body is detected by a perforation detecting means or the like. If the perforations exist in the film, a mask plate for setting the photographing picture size is moved inwardly of the same perforations by a mask plate driving means. Photographing is thus effected with the convectional standard photographing picture size. If no perforations exist in the film, the mask plate for setting the photographing picture size is located outwardly of a portion corresponding to the same perforations by the same mask plate driving means. The photographing can be performed with a photographing picture size larger than the standard size described above.
Then, it is thus possible to reduce an enlargement ratio during printing by enlarging the photographing picture by use of a film from which the perforations of the JIS-135 type film are eliminated. A high quality print picture can be also obtained.
By the way, the photographing picture size changeover camera disclosed in Japanese Patent Application No. 200877/1991 was proposed on the premise that the lens is not interchanged as in the case of, e.g., a compact camera. A photographing lens designed to have an image circle larger than the conventional one is previously installed in the camera body. Both photographing based on the ordinary picture size and photographing based on a picture size larger than the ordinary picture size are attainable.
However, when the S-format film having the large picture size is applied to a single-lens reflex camera, the following inconveniences arise.
As is known well, in contrast with the compact camera, the single-lens reflex camera provides a facility to the user by making usable a variety of interchangeable lenses having a compatibility. Hence, the conventional photographing lens is installed in the camera body in which the photographing lens having the image circle larger than that of the conventional photographing lens is installable. The photographing is effected in a state where picture size larger than the conventional standard picture size is set. In such a case, there is a remarkable decline in quality of an image of the image circle which covers the conventional picture size.
This trouble is caused due to an omission to switch over setting of the picture size to the conventional standard picture size on the occasion of installing the photographing lens having an image circle larger than that of the conventional photographing lens to perform photographing with the large picture size and next interchanging it to a photographing lens having a smaller image circle.
On the other hand, Japanese Patent Publication No. 14234/1961 discloses a technical means for simultaneously changing over both the photographing picture size by using a mask plate and the finder window. According to this technical means, in the same camera, the photographing operation is performed by changing a magnitude of the photographing picture size on demand with a manipulation from the outside of the camera body in accordance with a purpose of the photographing. An interval between the respective photographing pictures is thereby kept constant. In addition, the magnitude of the photographing picture size is displayed in the finder window. This technical means does not, however, imply that the photographing picture size varies corresponding to a difference between the image circles.
Proposed further in Japanese Patent Laid-Open No. 48054/1989 is a picture size changeover camera constructed to prevent an erroneous change in the film wind quantity per frame in the midst of photographing which uses the same roll film. This camera does not, however, imply that the photographing picture size varies corresponding to a difference between the image circles.